Bacterial vaginosis is a complex multi-microbial infection associated with the depletion of lactobacilli, the major flora of a healthy vagina and the overgrowth of Gardnerella vaginalis, Peptostreptococcus spp. and Prevotella bivia. BV may lead to premature labor. Endotoxins produced by the BV-associated bacteria cause serious brain/CNS damage in developing fetuses. Healthy vaginal Lactobacillus rhamnosus strain 160 produces an antimicrobial peptide, bacteriocin, designated as lactocin 160, which is active against BV associated microorganisms. We will examine our major hypothesis that this novel ribosomally-synthesized peptide is a potent antimicrobial agent for the prophylaxis and treatment of BV through the following three specific aims. We will determine lactocin 160's stability, safety, and spectrum of antimicrobial activity against BV associated vaginal pathogens. We expect lactocin 160 to be stable (alone and in combination with the selected natural antimicrobials), to have a broad range of antimicrobial activity against vaginal pathogens, and to be safe for human use (Specific Aim 1). Investigation of the mechanism of action by which lactocin 160 inhibits BV-associated microorganisms will lead to the understanding of the interaction between the cellular membrane and the peptide. We will determine whether one or both components of the Proton Motif Force are inhibited by lactocin 160 and if its activity is voltage-dependant, in other words, influenced by the growth phase of the pathogens. We will find out if ATP in the bacteriocin-treated cells will be hydrolyzed intracellularly, or will leak off the cell (Specific Aim 2). Finally, we will prove that lactocin 160 has increased bactericidal activity against vaginal pathogens at low pH established specifically by lactic acid and when combined with synergistically acting natural and safe antimicrobials such as Zn lactate, saponin, and Poly- lysine, all of which have a mechanism of antimicrobial action different from lactocin 160 (Specific Aim 3). Our research will lead to a new approach for BV prophylaxis and treatment.